Swain Stephen M, Muller Andrea J, Singh Davinder P
Commonwealth Scientific and Industrial Research Organization Plant Industry, Private Mail Bag, Merbein, Victoria 3505, Australia.
Plant Physiol. 2004 Feb;134(2):694-705. doi: 10.1104/pp.103.031666. Epub 2004 Feb 5.
Ectopic expression in Arabidopsis of a pea (Pisum sativum) cDNA (2ox2) encoding a gibberellin (GA) 2-oxidase (PsGA2ox2), involved in the deactivation of biologically active GAs, has been used to establish a role for GAs in promoting pollen tube growth. One line, 35S:2ox2/28c, when homozygous for the transgene, exhibits a novel small fruit phenotype. The 28c transgene reduces pollen tube growth, and this results in a reduced number of fertilized seeds that are only present at the end of the silique nearest the stigma. To confirm that the 28c pollen tube phenotype is due to sense expression of the 2ox2 mRNA, a "hairpin" RNA interface silencing construct, designed to silence 2ox2 expression, has been used to restore pollen tube growth and fruit development. The interaction between 28c and other mutants with increased GA response has also been examined to provide further evidence that GAs play an important role in pollen tube growth. Based on the ability of mutant alleles to suppress the 35S:2ox2/28c phenotype, we define new roles for the gar2-1 and rga alleles in GA signaling during pollen tube elongation in addition to their previously established roles in vegetative tissues. In contrast to the constitutive GA response observed in internodes and leaves lacking RGA and GAI, the rga-2 gai-d5 mutant combination is only a partial suppressor of the 28c phenotype. Because the dominant dwarfing gai-1 allele reduces GA response in vegetative tissues, its effect on plant fertility has been examined. Although gai-1 reduces seed set, this appears to reflect defects in reproductive development other than pollen tube function. Finally, we show that the genetic background (Landsberg erecta or Columbia) modifies the 28c phenotype and that this effect is not due to the ER/er difference between these two ecotypes.
将编码赤霉素（GA）2 -氧化酶（PsGA2ox2）的豌豆（Pisum sativum）cDNA（2ox2）在拟南芥中异位表达，该酶参与生物活性GA的失活，已被用于确定GA在促进花粉管生长中的作用。一个株系35S:2ox2/28c，当转基因纯合时，表现出一种新的小果实表型。28c转基因降低了花粉管生长，这导致受精种子数量减少，且仅存在于最靠近柱头的角果末端。为了证实28c花粉管表型是由于2ox2 mRNA的正义表达所致，一种设计用于沉默2ox2表达的“发夹”RNA干扰构建体已被用于恢复花粉管生长和果实发育。还研究了28c与其他GA反应增强的突变体之间的相互作用，以进一步证明GA在花粉管生长中起重要作用。基于突变等位基因抑制35S:2ox2/28c表型的能力，我们确定了gar2 - 1和rga等位基因在花粉管伸长过程中GA信号传导中的新作用，此外它们在营养组织中还有先前已确定的作用。与在缺乏RGA和GAI的节间和叶片中观察到的组成型GA反应相反，rga - 2 gai - d5突变体组合只是28c表型的部分抑制子。由于显性矮化gai - 1等位基因降低了营养组织中的GA反应，已研究了其对植物育性的影响。尽管gai - 1降低了结实率，但这似乎反映了生殖发育中的缺陷，而非花粉管功能缺陷。最后，我们表明遗传背景（Landsberg erecta或Columbia）改变了28c表型，且这种效应不是由于这两个生态型之间的ER/er差异所致。
